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path: root/autoutils/batches.go
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/*
Copyright (C) 2019 Leo Tenenbaum

This file is part of AutoArt.

AutoArt is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

AutoArt is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with AutoArt.  If not, see <https://www.gnu.org/licenses/>.
*/

package autoutils

import (
	"fmt"
)

/*
This function runs f in batches of batchSize. n will be the number in the
sequence. f should send an error to errs if it wants this function to return
that error, and otherwise should send nil when it is done. Before each batch,
a message will be printed, starting with progress, and showing how many batches
have been completed so far out of the total number of batches.
*/
const batchSize = 32

func RunInBatches(number int64, progress string, f func(n int64, errs chan<- error)) error {
	nBatches := number / batchSize
	errs := make(chan error)
	for batch := int64(0); batch <= nBatches; batch++ {
		fmt.Println(progress, batch+1, "/", nBatches+1)
		thisBatchSize := batchSize
		if batch == nBatches {
			// Deal with case of last batch
			thisBatchSize = int(number - nBatches*batchSize)
		}
		for task := 0; task < thisBatchSize; task++ {
			go f(int64(task)+batchSize*batch, errs)
		}

		for completed := 0; completed < thisBatchSize; completed++ {
			err := <-errs
			if err != nil {
				return err
			}
		}
	}
	return nil
}